Rotary latching mechanisms are used to provide controlled access to enclosures with examples ranging from electronics enclosures, vehicle compartments, control rooms etc. Typically a rotary mechanical latch finds application in locking mechanisms for securing the access panels, doors, lids and hatches to an interior volume of a controlled space. In one exemplary non-limiting application, the knob of a door acts as a driving device for applying torque to a rotating shaft that is coupled to a bolt mechanism for withdrawing the bolt from a corresponding strike plate located on the frame of the door. In this and other applications of rotary latching mechanisms, there is a need to prevent rotation of actuating shaft by unauthorized users and a further need to provide the drive input from a remote location (e.g. by electrical drive apparatus). Additionally there is a need for rotary latching mechanisms that provide positive latching of the actuating shaft in an unpowered state (e.g. passive latching) and are resistant to false unlatching of the actuating shaft due to vibrations in the environment of the latch. The present invention meets these needs by providing a positive rotary latching mechanism that is unlatchable by application of a drive torque to lock and unlock a cam arm attached to a rotary actuation shaft, where the cam arm is latched and unlatched by the cooperative positioning of leading and trailing cams incorporated into the drive mechanism.